1. Field of the Invention
This invention relates to a variable focal length lens in which the refractive power of a single lens itself can be fluctuated.
2. Description of the Prior Art
As a variable focal length lens of this type, there is known one in which the shape of the refracting surface is varied by deformation of an elastic member constituting the lens or by a variation in the pressure of liquid enclosed in an elastic film as shown in U.S. Pat. No. 3,664,727, or one in which the refractive index of the lens medium itself is varied by the use of liquid crystal or the like as shown in U.S. Pat. No. 4,190,330. However, the one in which the shape of the refracting surface is varied has a disadvantage that the variation in the shape is complicated and the control thereof is difficult, and the one in which the refractive index of the lens medium is varied has a disadvantage that the variable amount of the refractive power is small.